1. Field of the Invention
The present invention relates to a starter for an engine and, more particularly, to a coaxial type starter used to start an engine of a vehicle.
2. Description of the Prior Art
A conventional starter used to start an engine of a vehicle has heretofore been arranged as shown in FIG. 3.
The conventional starter 1 shown in FIG. 3 comprises a d.c. motor 2, an overrunning clutch 4 slidably fitted on an output rotary shaft 3, a reduction gear 5 arranged to transmit the rotational force derived from an armature rotary shaft 2a of the d.c. motor 2 to a clutch outer member 4a of the overrunning clutch 4 after reducing the speed thereof, and a shift lever 8 having one end thereof engaged with a plunger rod of an electromagnetic switch 6 disposed at one side of the d.c. motor 2 and the other end thereof engaged with an annular member 7 secured to the overrunning clutch 4 in order to cause the overrunning clutch 4 to slide on the output rotary shaft 3.
Thus, the conventional starter 1 needs the shift lever 8 in order to cause the overrunning clutch 4 to slide on the output rotary shaft 3, and the electromagnetic switch 6 which actuates the shift lever 8 and also turns on the power supply for the d.c. motor 2 is disposed at the side of the d.c. motor 2, that is, the starter 1 has the so-called biaxial arrangement. Therefore, the types of engine layout that have been feasible when designing a vehicle have heretofore been restricted to a substantial extent.
In order to avoid the above-described problem, it has been proposed to dispose the electromagnetic switch at one axial end of the d.c. motor so that the starter may have a simple configuration such as a relatively long and narrow tubular shape. According to this proposition, the starter is basically arranged such that the armature rotary shaft of the d.c. motor is made hollow and a rod, for example, a plunger rod, of the electromagnetic switch which has heretofore been used to actuate the shift lever is passed through the passage formed inside the armature rotary shaft so as to extend as far as the output rotary shaft. Since the armature rotary shaft of the d.c. motor and the rod of the electromagnetic switch are disposed on the same axis, this starter is known as the coaxial type starter.
The above-described coaxial type starter has a simplified overall configuration, that is, a relatively long and narrow tubular shape, but it suffers from the problem that, since the electromagnetic switch is disposed at the rear end of the d.c. motor, the overall length of the starter is increased by a large margin.